using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    class FtpConnection
    {
                                public TextBox TB;     // this is the public variable that will point to your form's textbox


        public void DoThis()
        {
            if (TB != null)
                TB.Text = "Some FTP Info...";
        }
    }
}

            FtpConnection con = new FtpConnection();
            con.TB = this.txtFtpLog;
            con.DoThis();

using System;

namespace DreamInCodeStuff
{
    // First we create an EventArgs class defining the information we'll pass back to the subscribing form...
    public class FtpMessageEventArgs : EventArgs
    {
        // Here we are defining two strings to send, but you could send any data...
        // (I added the stamp just to illustrate that you can pass more than just the string for the textbox)
        private string dtTmStmp;
        private string msg;

        // This constructor fills the variables when the instance is created...
        public FtpMessageEventArgs(string dateTimeStamp, string message)
        {
            dtTmStmp = dateTimeStamp;
            msg = message;
        }

        // These readonly properties allow the subscribing form to get the info you are passing...
        public string DateTimeStamp
        {
            get { return dtTmStmp; }
        }
        public string Message
        {
            get { return msg; }
        }
    }

    // Next we have to create a delegate. This defines what our event method needs to look like.
    public delegate void FtpMessageEventHandler(object sender, FtpMessageEventArgs mArgs);


    class FtpConnection
    {
        // Here we declare our event based on the delegate we defined earlier.
        // We make the event public so that anyone using our class can subscribe
        // to it with their own handler routine...
        // Basically, this is just a pointer to a method on the subsrcibing form.
        // (Just like we made a TextBox TB to point to a textbox on a form
        //  when we did this the *EASY* way)
        public event FtpMessageEventHandler MessageReceivedEvent;

        // Here is your public method for testing the whole thing...
        public void DoThis()
        {
            string message = "Some FTP Info...";
            FtpMessageEventArgs tmArgs = new FtpMessageEventArgs(DateTime.Now.ToLocalTime().ToString(), message);
            // Make sure the event has been subscribed to (it actually points to a method.)
            if (MessageReceivedEvent != null)
                MessageReceivedEvent(this, tmArgs);
        }

    }
}

using System;
using System.Windows.Forms;

namespace DreamInCodeStuff
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // Here we define a method with the same return type and parameters as the FtpConnection classes event.
        // We will assign this method to the public event on the FtpConnection class.
        private void FtpMessageReceived(object sender, FtpMessageEventArgs args)
        {
            string timeStamp = args.DateTimeStamp.Trim();
            string message = args.Message.Trim();
            txtFtpInfo.Text = timeStamp + ": " + message;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            FtpConnection con = new FtpConnection();
            // Point the event to our local method
            con.MessageReceivedEvent += new FtpMessageEventHandler(FtpMessageReceived);
            // test it..
            con.DoThis();
        }
    }
}